Ammonite

Object/Artifact

Crater Rock Museum

Name/Title

Ammonite

Entry/Object ID

78.57.175

Description

Crystal System: Hexagonal System Description: Phylum: Mollusca Class: Cephalopoda Subclass: Ammonidea Common Name: Ammonite Age: Devonian to Cretaceous Location: near Yreka, California Description: One tightly-coiled cast of an ammonite, showing ridges and some suture pattern. Color is light beige to pale green. Physical Characteristics: Ammonites are an extinct group of marine invertebrate animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs are more closely related to living coleoids (i.e. octopuses, squid, and cuttlefish) than they are to shelled nautiloids such as the living Nautilus species. Ammonites are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific geological time periods. Their fossil shells usually take the form of planispirals, although there were some helically-spiraled and non-spiraled forms (known as heteromorphs). The name ammonite, from which the scientific term is derived, was inspired by the spiral shape of their fossilized shells, which somewhat resemble tightly coiled rams' horns. Pliny the Elder (d. 79 AD. near Pompeii) called fossils of these animals ammonis cornua ("horns of Ammon") because the Egyptian god Ammon (Amun) was typically depicted wearing ram's horns. Often the name of an ammonite genus ends in -ceras, which is Greek for "horn". Fracture: Conchoidal Grain Size: Fine Hardness: 3 Calcite Kingdom: Animalia (Animals) Luster: Vitreous Class: Cephalopopda Phylum: Mollusca Rock Origin: Terrestrial Rock Type: Sedimentary Streak: white Subfamily: Ammonoidea

Collection

Fossil Collection

Acquisition

Accession

78.57

Source or Donor

Delmar Smith Fossil Collection

Acquisition Method

Donation

Dimensions

Width

7-11/16 in

Depth

1-3/8 in

Length

9-3/8 in

Location

Shelf

CS-H-4

Room

Curation Storage

Building

Crater Rock Museum

Date

February 3, 2024